Although Arc Euro are no longer are in business, no doubt you will find that Axminster or naybe Chester sell the SC4, so may be able to supply.
Alternatively, if you know the dimensions and Module number of the gears (possibly 1 or 1.25 Module); you might fond another lathe uses gears that are dimensionally the same (Warco, Sealey, or if you are in USA, possibly Grizzly. If antipodean, there may be an importer of a lathe using similar gears)
Howard